Some processors can operate in multiple modes, such as an active mode and a low power or sleep mode. In an active mode, a voltage regulator provides a voltage to the processor that allows the processor to execute instructions and perform normal operations. In the low power mode, the voltage regulator provides a retention voltage to the processor that allows the processor to retain its internal state, but not execute instructions or other normal operations. The retention voltage is lower than the voltage provided in the active mode, thereby allowing the processor to conserve power. The processor can enter the low power mode to conserve power but retain its internal state so that when it returns to the active mode it is able to continue operations from the state it had prior to entering the low power mode.
Some processors can support a coherent memory space or allow other modules of a device to access the processor cache. In order to perform cache transactions to maintain coherency or to service access requests from other modules received while the processor is in low-power mode, conventional processors switch from the low-power mode to the active mode. However, due to physical characteristics of the voltage regulator, the processor cannot quickly change from the low power mode to the active mode. Thus, conventional processors typically enter the low-power mode less frequently as more cache transaction requests are received, and therefore are in the low power mode less often. This can result in an undesirable consumption of power by the processor. Accordingly, there is a need for a new processing device and methods.